The present invention relates to a driving mechanism for plank clamp, in which a coupling arm is pivotally turned to rotate a gear set and to backward move a rack meshing with the gear set, so that a movable jaw connected to a free end of the rack is moved toward a clamp main body of the plank clamp.
FIG. 1 shows a conventional plank clamp currently available in the markets. A driving mechanism for the conventional plank clamp includes a pivotally turnable trigger A connected to a fixed jaw of the plank clamp and provided with a groove B, and an extension bar D movably connected to the fixed jaw of the plank clamp and having a movable jaw C fixedly connected to a free end thereof. When the trigger A is pivotally turned, the groove B is brought into an inclined position to get in tight contact with and push against the extension bar D to move the same, so that the movable jaw C could be shifted to a desired position relative to the fixed jaw.
A disadvantage of the above-described driving mechanism for the conventional plank clamp of FIG. 1 is that the extension bar D is moved through a tight frictional contact of the inclined groove B on the pivotally turned trigger A with the extension bar D to push the latter, and a user needs to apply a considerably big force to turn the trigger A and frictionally push the extension bar D. Thus, the user""s hand operating the trigger A would soon become sore and stiff.
It is therefore a primary object of the present invention to provide an improved driving mechanism for plank clamp to eliminate the drawback existing in the conventional plank clamp.
The driving mechanism for plank clamp according to the present invention mainly includes a gear set and a rack mounted on a clamp main body to mesh with each other, a first sleeve tightly mounted on a rotary shaft of the gear set, and a coupling arm mounted on a shank of the first sleeve. When the coupling arm is pivotally turned about the rotary shaft toward the clamp main body, the first sleeve and the gear set are caused to rotate at the same time, and the rack meshing with the gear set is caused to move backward toward the clamp main body. A movable jaw fixedly connected to a free end of the rack is therefore moved toward the clamp main body, which also function as a fixed jaw of the plank clamp, to a desired position to tightly clamp a plank between it and the clamp main body.